BACKGROUND: Incorporating plant-based diets as a supplement to medical treatment may have a beneficial impact on patients with Crohn's disease, however, research with intervention studies is required. OBJECTIVE: To investigate the feasibility of a plant-based diet intervention. Secondly, the purpose was to investigate whether such diet may reduce disease activity and enhance quality of life. MATERIALS AND METHODS: This study was designed as a single arm feasibility study. Outpatients with Crohn's disease in biological therapy were guided over twelve weeks towards a dietary lifestyle change. OUTCOME MEASURES: Feasibility concerning recruitment, retention rate and compliance. Secondary outcomes were measures of patient reported outcome questionnaires (PROMS). Paired t-tests were used to examine changes in CO2 emissions, anthropology, biomarkers, and patient-reported data. Δ-values were used to investigate difference between dietary intake and requirements. Linear regression analyses examined the association between biomarkers and PROMS. RESULTS: In total, 15 participants completed the intervention with easy recruitment and a retention rate at 87.6%. A clinically positive tendency was seen towards improved symptom scores for disease (HBI; p=0.028 and IBDQ; p=0.006) but not for fatigue (IBD-F; p = 0.097), although none of these were statistically significant. Adverse effects were decreased protein intake (p=0.069) and slightly reduced muscle mass. It remains unclear to what extent the intervention contributed to the improved self-reported effects although perception of disease activity was improved. CONCLUSION: This study demonstrates that it is possible to retain patients following a plant-based diet. However, the dietary change required ongoing dietetic support with a focus on anti-inflammatory agents and the still unattainable protein requirements.